Cameras in vehicles for detecting the surroundings of a vehicle may be used in particular in driver assistance systems for functions such as night vision assistance, lane departure warning, traffic sign recognition, lighting assistance, and/or vehicle backup assistance.
The use of cameras for rain sensor systems in vehicles is also known. Published German patent application document DE 197 49 33 A1 discloses a method and a camera for detecting objects, such as water droplets or other soiling, present on a windshield of a motor vehicle. The camera is situated behind the windshield and is focused on the exterior of the windshield.
Camera systems are also known which are suitable for recording the surroundings of a vehicle as well as detecting a state of a vehicle window pane. Such a camera system is described in published German patent application document DE 10 2004 015 040 A1. This camera system includes a camera and a radiation source, the camera having an image sensor for recording images with the aid of which a first optical radiation generated by the vehicle surroundings is detectable, and the radiation source generating a second optical radiation which is detected by the image sensor. The second optical radiation which is detected by the image sensor is a function of the state of the window pane, in particular wetting of the window pane by raindrops. To achieve such a dependency, the second optical radiation which is emitted by the radiation source is coupled into the interior of the vehicle window pane in such a way that in the unwetted state of the vehicle window pane the second optical radiation undergoes one or multiple total reflections before a portion of the second optical radiation is coupled into the camera. The total reflection, and therefore the intensity of the second optical radiation which is detectable by the image sensor, is reduced as a result of wetting of the surface of the vehicle window pane. The measurement of this reduction may be used to ascertain the wetting of the vehicle window pane.
According to published German patent application document DE 10 2004 015 040 A1, the beam bundle of the second optical radiation which strikes the image sensor is shaped in such a way that only a small partial area of a sensor surface of the image sensor is irradiatable by the second optical radiation. The image data encompassed by this partial area are used to determine the state of the window pane. The remaining area of the sensor surface of the image sensor is used for recording the vehicle surroundings. The partial area of the image sensor which is irradiatable by the second optical radiation is concealed by a shutter in such a way that first optical radiation originating from the vehicle surroundings is blocked and is not able to strike this partial area. Such a camera system requires accurate guiding of the second optical radiation so that the latter does not irradiate the partial area of the sensor surface which is provided for detecting the vehicle surroundings. Furthermore, as a result of providing a shutter, the portion of the sensor surface of the image sensor which is available for detecting the vehicle surroundings, i.e., first optical radiation, is reduced. A shutter also represents an additional element for the camera system.